Mozilla has announced the release of Firefox 8 for Windows, Mac, Linux and Firefox for Android. This release appears to be a relatively minor update. Perhaps the main feature of this update is the ability for user control over third-party addons. "At Mozilla, we think you should be in control, so we are disabling add-ons installed by third parties without your permission and letting you pick the ones you want to keep." A detailed technical description of this new Firefox release can be found in the release notes.

versions are irrelevant. Mozilla does not care about versioning. If they did they'd keep 4.3 to avoid the bad mouthing from people like you.
What they care about is being able to push changes faster, because otherwise they can't keep up.
Example, Google docs using new "HTML5" apis, that only Chrome would support for 6month? That's not possible to compete without updating.
There's a ton of other such examples. Like SPDY too. Heck we wouldn't have websockets working right now.

And yeah, Opera has a low % userbase, guess why. They will have to keep up, too.